1. Field of the Invention
This invention relates generally to fluid flow control valves and more particularly to an improved so-called capacity fuse valve which closes in response to a predetermined fluid flow volume through the valve. The invention relates also to novel flow control means and a novel temperature responsive actuator for the valve and other uses.
2. Discussion of the Prior Art
The valve of this invention belongs to the class of valves referred to as fuse valves because of their general similarity of purpose and operation to electrical fuses. Thus, a fuse valve is designed to be installed in a pressure fluid system between a pressure fluid source and a fluid receiver, such as a pressure fluid actuator, and to remain open as long as fluid flow through the valve is within a predetermined normal range. The valve closes to block fluid flow through the system in response to a predetermined flow quantity through the valve. The flow quantity to which some fuse valves respond is flow velocity. This type of fuse valve, which may be thought of as a velocity fuse valve, is designed to remain open as long as the flow velocity through the valve does not exceed a predetermined maximum velocity and to close if this maximum flow velocity is exceeded. Other fuse valves, referred to as capacity fuse valves, respond to total flow volume through the valves. Such a capacity fuse valve is intended for use in a fluid pressure system wherein fluid flow occurs intermittently and is designed to close in response to a predetermined total flow volume through the valve.
U.S. Pat. Nos. 2,821,209 and 4,465,093 disclose examples of known velocity fuse valves. U.S. Pat. No. 3,880,398 discloses a capacity fuse valve. Another capacity fuse valve is a so-called floating piston valve, one example of which is disclosed in U.S. Pat. No. 4,655,245.
Fuse valves, both velocity fuse valves and capacity fuse valves, are used for a variety of purposes. One particularly important use of such valves is in hydraulic systems, such as aircraft hydraulic systems, to prevent fluid loss, especially catastrophic fluid loss, in the event of a leak or fluid line rupture. In this application, the velocity fuse valve responds to the sudden increase in flow velocity through the valve resulting from a rupture in the fluid line containing the valve by closing the valve before substantial fluid loss can occur. In other words, the velocity fuse valve is designed to sense and then respond to an abnormally high flow condition. The purpose of a capacity fuse valve, on the other hand, is to pass or convey to a fluid actuator or other fluid receiver a volume of fluid which may vary within a normal volume range determined by the normal fluid requirements of the fluid receiver. The valve closes to prevent further flow through the valve if the total flow volume through the valve exceeds the predetermined upper limit of this normal volume range. Thus, a capacity fuse valve prevents rather than responds to an abnormal flow condition.